Brushless electro-mechanical machine

ABSTRACT

An electromotive machine comprises a stator element and a rotor element, the stator element including at least one set of four toroidally shaped electromagnetic members, the electromagnetic members arranged along an arc a predetermined distance apart defining a stator arc length. Each of the members has a slot, and the rotor element comprises a disc adapted to pass through the slots. The disc contains a plurality of permanent magnet members spaced side by side about a periphery thereof and arranged so as to have alternating north-south polarities. These permanent magnet members are sized and spaced such that within the stator arc length the ratio of stator members to permanent magnet members is about four to six. The electromagnetic members are energized in a four phase push-pull fashion to create high torque and smooth operation.

BACKGROUND OF THE INVENTION

[0001] The following invention relates to a brushless electromechanicalmachine for converting electrical energy into mechanical motion andvice-versa. More specifically, the invention relates to an electricmotor/generator having self-starting capabilities, high torque andincreased efficiency.

[0002] Electric motors employing brushes are characterized by lowefficiency and require elaborate starter mechanisms. Recently, a type ofbrushless motor has been developed which employs an electromagnet havinga stator comprised of a plurality of toroidal pole pieces. The polepieces each have a narrow gap to permit the passage of a disk shapedrotor. The rotor includes a plurality of permanent magnet members spacedabout the periphery of the disk. As the permanent magnet members passthrough the gap in the stator poles, the magnetic circuit is completed.With appropriate switching circuitry, this combination can be made tofunction as a brushless electric motor. An example of such constructionis shown in the U.S. patent to Porter, U.S. Pat. No. 5,179,307.

[0003] In the Porter motor, the permanent magnets on the rotor arewidely spaced apart. The rotor is a disk having permanent magnet memberssituated about its periphery and spaced 36° apart. The driving circuitryis triggered by combinations of light emitting diodes and photosensitivetransistors arranged on opposite sides of the rotor disk. Apertures inthe rotor disk permit light from and LED to fall on a photosensitivetransistor at appropriate points in the rotation of the rotor disk. Thiscauses the driving current to cause current to flow in the coil.

[0004] A problem with the motor of the '307 patent is that the permanentmagnets are spaced too far apart about the periphery of the rotor diskfor the machine to operate efficiently. This wide spacing of permanentmagnet members would require a large mass rotor operating as a flywheelwith enough energy stored in the rotor to provide considerablerotational momentum. A large mass rotor, however, would be impossible tostart without some type of auxiliary starter mechanism. Additionally,this motor cannot easily reverse its direction.

BRIEF SUMMARY OF THE INVENTION

[0005] The present invention provides a construction for anelectromotive machine which can be either an electric motor or agenerator. The electromotive machine includes a stator element and arotor element where the stator element includes at least one set of fourtoroidally shaped electromagnetic members where the electromagneticmembers are arranged spaced apart along an arc to define a stator arclength. Each of the electromagnetic members includes a slot and a rotorelement comprising a disk adapted to pass through the aligned slots ofthe electromagnetic members. The rotor contains a plurality of permanentmagnet members spaced side-by-side about a periphery of the disk andarranged so as to have alternating north/south polarities. The permanentmagnet members are sized and spaced such that within the stator arclength, the ratio of stator members to permanent magnet members is about4 to 6.

[0006] Although the electromotive machine of the invention will workwith one set of four toroidal electromagnets, a second set may bepositioned symmetrically along a circular arc defined by the first set.Additional sets of four toroidal electromagnetic members may be used ifdesired.

[0007] The machine includes at least one motor drive electronics modulefor energizing the toroidal electromagnetic members with currentaccording to a predetermined sequence. The sequence is triggered by Halleffect sensors placed adjacent the electromagnetic members along thearc. The Hall effect sensors sense changes in the magnetic field andprovides trigger signals to the electronics module so that theelectronics module can energize the electromagnetic members in apredetermined sequence. Since the ratio of electromagnet stator membersto permanent magnets on the outer periphery of the disk is about 4 to 6,the toroidal electromagnets are operated in push-pull fashion in whichswitching occurs when a pair of magnets passes the centerline of anelectromagnetic member.

[0008] The machine may also be operated in reverse as a generator usingthe rotor as a mechanical input device. In this configuration currentinduced in the coils by the turning of the rotor charges a battery. Inan automobile, for example, the machine may operate first as a startermotor and then switch over to an alternator.

[0009] The foregoing and other objectives, features, and advantages ofthe invention will be more readily understood upon consideration of thefollowing detailed description of the invention, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0010]FIG. 1 is a perspective schematic view of the electromechanicalmachine of the present invention.

[0011]FIG. 2 is a top view of the electromechanical machine of thepresent invention employing two sets of electromagnetic members.

[0012]FIG. 2A is a side cutaway view of FIG. 2 taken along line 2-2.

[0013]FIG. 3 is a schematic diagram of a drive module for use when theelectromechanical machine is being used as an electric motor.

[0014]FIG. 4 is a schematic diagram of a Hall effect sensor used inconnection with the electronic drive module of FIG. 3.

[0015]FIG. 5 is a partial plan schematic view of the electromechanicalmachine of FIG. 1.

[0016]FIG. 6 is a timing diagram illustrating the switchingcharacteristics of the electronic drive module of FIG. 3.

[0017]FIG. 7 is a partial perspective view of the electromechanicalmachine of the present invention configured as a linear actuator.

[0018] FIGS. 8A-8D represents a schematic view of the toroidalelectromagnetic members and the permanent magnet members illustratingthe four-phase switching characteristics of the electronics drivermodule of FIG. 3.

[0019]FIG. 9 is a partial top view of an electromotive machine of theinvention.

[0020]FIG. 10 is a schematic diagram of a circuit employing theinvention as a combination starter motor and alternator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0021] An electromechanical machine 10 is shown schematically in FIG. 1.The machine 10 includes a plurality of toroidally shaped electromagnets12. There are four such electromagnets 12 a, 12 b, 12 c and 12 d. Theelectromagnets 12 a-d are arranged along an arc having a predeterminedlength. Each of the electromagnets is toroidally shaped and each has agap 14 (refer to FIG. 2A). The gaps 14 are aligned which permits theouter edge of a wheel or disk 16 to pass through them. The disk 16 hasan output shaft 18 which may be coupled to any suitable device such as afan or a tub for a washing machine (not shown). The output shaft couldalso be coupled to some source of rotational energy such as a driveshaft. In this configuration, the motor is initially used as a startermotor and then switches into a generator or alternator mode.

[0022] The disk includes a plurality of permanent magnet members 13 a,13 b which are arranged in alternate north-south polarity. The magnets13 a, b are sized and spaced so that within the stator arc length theratio of toroid electromagnets 12 a-d to permanent magnets 13 a, b isalways about 4 to 6. The permanent magnets are closely spaced, havingspaces between each adjacent magnet that does not exceed 10% of thediameter of the uniformly sizes magnets 13 a, b.

[0023] Referring to FIG. 2, if desired, two groups of electromagnetmembers 20 and 22, respectively, may be used. Each of the sets 20 and 22contains at least four (4) toroidal electromagnet members 22 a-d and 20a-d respectively. Further, if desired, more sets of electromagnetmembers may be used depending upon the type of application desired. Eachof the electromagnetic members in a set contains a slot and the slotsare aligned along an arc allowing the flywheel 24 to pass through theslots. As in the example of FIG. 1, the flywheel 24 includes a pluralityof permanent magnet members 26 having alternating north-south polaritiesabout the periphery of the flywheel 24 that are in all respects the sameas magnets 13 a, 13 b.

[0024] The electromechanical machine of the present invention may beconfigured to operate either as a motor or as a generator. For example,when acting as a motor or a motor/starter, the electromagnets 12 a-d areelectronically switched in polarity to attract and then repel theappropriate permanent magnets 13 a, b in the flywheel. This applies arotational force to the flywheel and spins the output shaft 18. Sincethere are no mechanical gears needed, the starting action is silent.Conventional automotive starter motors, however, are noisy. Once theengine is running, the machine can be converted to a generator bydecoupling the driving electronics module. The permanent magnets 13 a, bmoving past the electromagnets 12 a-d with the driving circuitry nowswitched off can be used to generate electrical power.

[0025] Toroidal cores are used for the electromagnets in this machinesince they are the most efficient transformer core configuration.Toroidal electromagnets are self-shielding since most of the flux linesare contained within the core. In addition, the flux lines areessentially uniform over the entire length of the magnetic path. Theslot 14 that is formed in each of the toroidal electromagnetic memberswould normally cause a decrease in flux density. However, the action ofthe moving permanent magnet members keeps the gap filled with permanentmagnet material and thus maintains the field integrity within the core.

[0026] Referring to FIG. 3, a pair of integrated circuits IC1 and IC2are coupled to two electromagnet members consisting of electromagnets 12a and 12 c. It will be appreciated that an identical electronics modulewould be used to drive electromagnets 12 b and 12 d. The ICs, IC1 andIC2, have output gates coupled to transistors Q1, Q2, Q3 and Q4respectively. IC1 and IC2 are half bridge MOSFET drivers which aretriggered by Hall effect sensor IC5, (refer to FIG. 4). The Hall effectsensor IC5 has its outputs coupled to the inputs of IC1 and IC2,respectively. Output line IC5, pin 2 is coupled to the input line at pin2 of IC1. Similarly, output line IC5, pin 3 is coupled to input line 2of IC2. There is another Hall effect sensor (not shown) forelectromagnets 12 b and 12 d which operates the same way but which ispositioned so as to generate its signal at a phase angle which lags thesignal from

[0027] IC5. The result is that electromagnetic member pairs areenergized 180° out of phase with each other. This is illustrated by thetiming diagram of FIG. 6.

[0028]FIG. 6 shows a four-phase timing diagram that repeats for every10° of rotation of the rotor 16. The magnets 13 a, b are spaced 10°apart while the electromagnetic members 12 a-d are spaced 15° apart. Thetiming relationship between the magnets and the coils is shown best inFIGS. 8A-8D.

[0029] The arrows in FIG. 8 for each phase indicate the lines ofattraction and/or repulsion between the permanent magnets and the coilsbased upon the polarity of the energizing current from the driver modulepairs of IC's of FIG. 3. FIG. 8 illustrates schematically the waveformof FIG. 6. IC1 and IC2 generate driver currents 180° out of phase sothat when coil 12 a is high, 12 c is low and vice versa. Another drivermodule pair of IC's (not shown) does the same thing with coils 12 b, 12d but out of phase with respect to toroidal coils 12 a, 12 c by 5°. TheHall sensors are placed along the stator in advance of the rotor and arespaced apart by 5° in order to trigger their respective IC's at a phaseangle difference of 5°. The result is a very smooth rotor drive madepossible by the sizing and spacing of the magnets so that the ratio ofcoils to magnets within the arc length of the electromagnet members 12a-12 d is always 4 to 6. Thus, a pair of alternate north-south polemagnets are experiencing opposite polarity fields when they are centeredwithin the gaps of alternate electromagnets 12 a, 12 c, whilenorth-south pairs of magnets, each halfway within the slots of the otherpair of electromagnets 12 b, 12 d, are experiencing the switching of thepolarity of current through those electromagnets 12 b, d.

[0030] Referring to FIG. 7 the machine of the present invention may beoperated as a linear actuator. In this embodiment the magnets may be ofa rectangular shape. In this case, the stator arc length is measuredalong a straight line and it should be understood that the term statorarc length need have no particular shape as it may be used withstator/rotor configurations of differing types. In addition, the magnetsneed have no particular shape to be effective. As long as the ratio ofelectromagnetic members to permanent magnets is about 4 to 6 within thearc length occupied by the stator coils, the invention will operate asdesired.

[0031] Referring to FIG. 9, the Hall sensors IC5 and IC6 are spacedapart by 5° radially so that trigger signals will be generated in theproper phase with each other. The Hall sensors are affixed to a statorhousing (not shown). It can be appreciated from FIG. 9 that the term“stator arc length” includes an arc that is slightly longer than thelength between each end of the 4 electromagnets 12 a-d and includesareas where the fields generated by those electromagnetic membersinfluence the permanent magnets 13 a, b. In FIG. 9, this area isindicated by the dashed lines. Although the arc in FIG. 9 has been shownas substantially a straight line, it is to be understood that it mayrepresent either a linear device or a circular arc.

[0032] Referring to FIG. 10, a rotor or flywheel 50 is coupled to ashaft 52 which may in turn be coupled to the drivetrain of an automobile(not shown). Permanent magnets 54 a (North polarity) and 54 b (Southpolarity) are situated about the periphery of the rotor 50. A statormodule 56 is situated adjacent the rotor 50 and includes a set of fourtoroidal electromagnetic members having substantially the sameconfiguration as shown in FIG. 1. A switching module 58 switches betweena circuit that accepts an input from a motor drive module 60 and onethat provides an output to a rectifier and regulator module 62. Theregulator module 62 charges a battery 64.

[0033] Signals on input lines labeled “start” and “run” respectivelycontrol the function of the switching module 58. In the start mode acircuit like the circuit of FIG. 3 is turned on in the switching module.Once the motor (not shown) has been turned on, a signal is provided tothe “run” line turning off the circuit of FIG. 3 and allowing currentfrom the stator module 56 to flow directly to the rectifier andregulator module 62.

[0034] The terms and expressions which have been employed in theforegoing specification are used therein as terms of description and notof limitation, and there is no intention, in the use of such terms andexpressions, of excluding equivalents of the features shown anddescribed or portions thereof, it being recognized that the scope of theinvention is defined and limited only by the claims which follow.

1. An electromotive machine comprising a stator element and a rotorelement, the stator element including at least one set of fourtoroidally shaped electromagnetic members, said electromagnetic membersarranged along an arc a predetermined distance apart defining a statorarc length, each of said members having a slot, the rotor elementcomprising a disc adapted to pass through said slots, said disccontaining a plurality of permanent magnet members spaced side by sideabout a periphery thereof and arranged so as to have alternatingnorth-south polarities, the permanent magnet members being sized andspaced such that within said stator arc length the ratio of statormembers to permanent magnet members is about four to six.
 2. Theelectromotive machine of claim 1, further including at least a secondset of four toroidally shaped electromagnet members positionedsymmetrically with respect to said first set along said arc.
 3. Theelectromotive machine of claim 1, further including at least one motordrive electronics module for energizing said set of electromagnetmembers with current according to a predetermined sequence.
 4. Theelectromotive machine of claim 3, further including Hall effect sensorssituated adjacent selective ones of said electromagnetic members andproviding trigger signals to said electronics module to enable saidelectronics module to execute said predetermined sequence.
 5. Theelectromotive machine of claim 1 wherein each of said permanent magnetmembers are spaced about 10° apart as measured between radial linesextending through a center of each magnet member.
 6. An electromotivemachine comprising (a) a stator assembly including at least oneelectromagnet module, said electromagnet module comprising at least fourelectromagnetic members spaced about 15° apart, each of saidelectromagnetic members having a slot, said electromagnetic membersarranged side by side wherein said slots are aligned with each other,and (b) a rotor assembly comprising a rotary member having a periphery,the rotary member including a plurality of permanent magnet membersarranged about said periphery side by side in alternating north-southpolarities and spaced about 10° apart.
 7. The electromotive machine ofclaim 6, further including a driver circuit coupled to saidelectromagnet module for energizing said electromagnetic members in analternating polarity sequence.
 8. The electromotive machine of claim 7,further including Hall effect sensors spaced along said lineal spaceadjacent to said permanent magnet members for providing trigger signalsto said driver circuit.
 9. The electromotive machine of claim 6 whereinsaid stator assembly includes at least a pair of electromagnet modules.10. The electromotive machine of claim 9 wherein said rotary member is adisk or wheel.
 11. The electromotive machine of claim 10 wherein saidpermanent magnet members are disc-shaped.
 12. The electromotive machineof claim 13 wherein each permanent magnet member has a diameter, and aspacing between adjacent permanent magnet members does not exceed 10% ofsaid diameter.
 13. The electromotive machine of claim 6 wherein thestator and rotor assemblies are configured as a linear actuator.
 14. Theelectromotive machine of claim 6, further including a switching modulefor switching said driver circuit off and for coupling an output of saidstator assembly to a rectifier circuit for charging a battery.
 15. Theelectromotive machine of claim 1, further including a drive circuit forproviding drive current to said electromagnetic members thereby causingsaid rotor to rotate, and a switching module for turning off said drivecircuit thereby allowing said stator module to provide current to chargea battery.